Development of silver halide emulsions in color



Patented Feb. 7, 1939 DEVELOPMENT OF SILVER HALIDE EMULSIONS IN CQLOR Gustav Wilmanns, Wolfen kreis Bitterfeld, and

Wilhelm Schneider, Dessau, Germany, assignors to Agfa Ansco Corporation, Binghamton, N. Y., a corporation of New York No Drawing. Application April 16, 1936, Serial No. 74,816. In Germany April 1'7, 1935 3 Claims.

Our present invention relates to development of silver halide emulsions in color.

One of its objects is to provide a process of developing silver halide emulsions in color.

5 Further objects will be seen from the detailed specification following hereafter.

It is known that silver halide layers can be developed in colors. For this purpose there have been used para-aminophenol or dialkyll0 amino-aniline in admixture with phenol, aniline or such substances as contain a methylene-group capable of reaction. The picture obtained contains silver and the dyestuff, the latter being a quinone-imine dyestufi or an azomethine, accordla ing to the nature of the selected components.

Another process consists in using certain polyhydric phenols, such as pyrocatechol or pyrogallol, in an alkaline solution without a sulphite. Both processes suffer from the disadvantage that the solutions have little stability; moreover, the last-named developers give tints which are not very pleasing.

The present invention depends on the observation that very beautiful pictures in colors are obtained when an ortho-methyl-aminophenol or a. substitution product thereof acts on the silver halide layer in a solution alkaline with alkali carbonate or caustic alkali. After separating the silver, for example with Farmers reducer.

o thepure dyestufl picture remains. The developing solutions are remarkably stable. The substituents may be alkyl, such as methyl or ethyl, halogen, alkoxy, such as methoxy or ethoxy, or an aminogroup, or a. dialkyl amino-group, such as a dimethylamino-group or a diethylamlnogroup. The compounds containing halogen as a substituent have proved to give the best effect.

Suitable ortho-methylaminophenols are, for instance, ortho-methylaminophenol giving a yellow color, 4-chlor-ortho-methylaminophenol giving a brown color, 5-chlor-ortho-methylaminophenol and 4,5-dimethyl-ortho-methylaminophenol giving a yellow color, 4-chlor-6-aminoortho-methylaminophenol giving a brown color,

and 4-6-dimethyl-ortho-methylaminophenol giving a yellow color.

The following examples illustrate the "wention:-

Example 1.--A yellow developer is afforded by the following solution:

4 5-dimethyl-2-methyl-aminophenol-gram- 1 Sodium hydroxide--- Water cc 200 Example 2.-A yellow-red picture is obtained by means of the following developer:

2-methylaminophenol gram 1 Potassium carbonate grams 10 Water cc 200 Example 3,--A red picture is obtained by means 15 of the following developer:

4-chloro-2-methylaminophenol grams 2 Potassium carbonate do 15 Water 00.. 200

What we claim is:

1. A process of developing an exposed silver halide emulsion in color, which comprises depositing a dyestuif on the exposed silver halide by treating the exposed silver halide emulsion with a developing solution consisting of an orthomethylaminophenol, water and an alkali selected from the class consisting of alkali carbonates and caustic alkalies.

the emulsion.

3. The process as defined in claim 2, wherein the orthomethylaminophenol is 4.5'-dimethyl-2- methylaminophenol.

GUSTAV WILMANNS. WILHELM SCHNEIDER. 

